1. Field of the Invention
The present invention relates to a multiprocessing computer system employing common memory and, more particularly, to sharing software code for multiple processors in a single, common non-volatile memory storage device.
2. Description of the Prior Art
Many digital electronic devices, such as computers, contain a central processing unit (CPU) for the majority of the computation required, and a coprocessor for lighter duty housekeeping chores. These processors require that all or a portion of their firmware instructions be stored in non-volatile storage since they must be executed immediately upon the application of power to "boot up" the system. Each processor requires such non-volatile storage to facilitate booting of the system. Multiple non-volatile storage devices have therefore been necessary within multiprocessing systems.
In addition to the required non-volatile storage, it is also desirable that the non-volatile storage device be reprogrammable in the field since firmware changes and improvements are inevitable. The support circuitry and additional cost required for multiple, non-volatile, reprogrammable storage devices can force the system designed to forego these desirable features to ensure system integrity.
In some known systems a separate non-volatile storage device is used for each of the multiple processors which increases the cost of the computer system. One method frequently used is to simply employ single chip microcomputers with on-chip memory for the light duty housekeeping chores. This on-chip memory is typically either ROM or EEPROM, both requiring a system disassembly to upgrade the firmware code contained in the memory. The need for multiple non-volatile storage devices in computer systems also adds to the cost of such systems.